We thank Zheng et al.  for their interest and positive comments on our recently published study in Anesthesiology.  We subscribe to their emphasis on the strong relation between perioperative atelectasis and ventilator-induced lung injury in anesthetized children. We agree that the best possible study design is a randomized controlled trial with a larger number of patients and including postoperative management. Our exploratory cohort study, however, was designed to assess the effects of capnoperitoneum on lung strain-stress in anesthetized children. By using a multimodal monitoring, we aimed at better understanding these mechanisms of ventilator-induced lung injury in children, and the responses to an individualized protective ventilation. While not suited for a randomized controlled trial, such a design provides essential information for the improvement and enrichment of future studies. As the authors clearly state, even in a more controlled experimental setup like ours, some children did not achieve a negative air test reinforcing the need of physiologic response–driven instead of pragmatic protocol–driven trials commonly used in randomized controlled trials.

Zheng et al. propose some principles to optimize lung protection in children, but many of them do not directly apply to the purpose of our study. They emphasize the importance of low tidal volume, over its combination with lung recruitment, and positive end-expiratory pressure, in lung protection.  However, several studies have now demonstrated that low tidal volume alone does not reduce postoperative pulmonary complications and thus should not be considered “per se” protective especially in the presence of atelectasis. Furthermore, recent adult studies showed that protective ventilation, combining low tidal volume, lung recruitment, and individualized positive end-expiratory pressure titration, decreased postoperative pulmonary complications in abdominal and thoracic surgery. Interestingly, these last studies included the use of continuous positive airway pressure and high-flow nasal oxygen in the postoperative period, to minimize atelectasis. Our study is in line with these findings, as a more holistic protective ventilatory strategy guided by multimodal monitoring decreased lung strain and improved lung function in anesthetized children.